Hydraulic starting system and valves therefor



Jan. 27, 1970. L. c. .nalwmmass E1 AL 3,491f795 HYDRAULIC STARTINGSYSTEM AND VALVES THEREFOR Original Filed Aug. 5. 1966 3 Sheets-Sheetv lATroRNExs Jan. 27,1970

n.. c. JENNINGS E1 A1.

HYDRAULIC STARTING SYSTEM AND VALVES THEREFOR Qriginal Filed Aug. 5.1966 5 Sheets-Sheet 2 INVENTRS 'LYSTON C. JENNINGS HOMRD C. SFOONERATTORNEYS Jan. 27, 1970 L. :.JENN1NGS ET AL HYDRAULIC STARTING SYSTEMAND VALVES THEREFOR Original Filed Aug. I5. 1966 I I iii!! 1 I 31| l l'n 347 r I 3251 331C l fafa \\\l 325e 3 325C 2331i; h 33m I?. 346 22@323 733nd 319 33| 331e 335 34% 33221)? 339 30Gb 31/8315 L33@ 322i:

Paw `332e b ,32h33, 33m 331g 3O3Q aow ab j H65 l FIG- 6. 1 2 1 3|5 l306m\ 5 Q/ 306k 7%? 335- m l 3530i/ K \%3061- 36k 3oef/ I 342/ 343 v 34|INVENTORS 3062 LYsToN CJENNINGS 306(O HOWARD C. SPOONER F166 ,303!) 5Sheets-Sheec 5 ATTORNEYS United States Patent O U.S. Cl. 137-609 4Claims ABSTRACT OF THE DISCLOSURE Valving device useful in a hydraulicstarting system employing an overcenter motor-pump unit which issupplied with motive fluid from an accumulator, and which causes themotoring-to-pumping selector control of the unit to maintain the latterin the motoring mode of operation as long as the start valve allowscommunication between the accumulator and the overcenter unit. Thevalving device pressurizes the selector control by allowing iiuid toilow to it from the accumulator, but vents this icontrol exclusivelythrough a separate exhaust path which is controlled by a valve that isactuated independently of accumulator pressure. Although the flow pathto the selector control can pass through the start valve, preferablythis path is controlled by a separate `valve which operates topressu'rize the selector control before the start valve opens to deliverhigh pressure motive uid to the overcenter unit. In any event, it alsois preferred that the start valve and the valving device be incorporatedin a unitary package.

This application is a division of application Ser. No. 569,921, filedAug. 3, 1966, now Patent No. 3,384,027.

This invention relates to hydraulic starting and pumping systems.

U.S. Patents 3,203,165, granted Aug. 31, 1965, and 3,234,889, grantedFeb. 16, 1966, disclose systems of this kind which employ overcentermotor-pump units and which use an accumulator as the source of motiveiluid for the starting operation. In each of these systems, thepositioning mechanism for the displacement control element of themotor-pump unit includes a fluid pressure control motor, a lpressureresponsive control valve having supply and exhaust positions in which itconnects the control motor with the high pressure side of the system andthe reservoir, respectively, and an actuating motor which is controlledby the engine start valve and which acts on the control valve in aid ofits normal pressure reaction surface. During the starting cycle, thestart valve connects the actuating motor with the high pressure side ofthe system for the purpose of holding the control valve in its supplyposition. On the other hand, during the pumping operation, the startvalve vents the actuating motor and thereby allows the control valve toperform its normal supply and exhaust functions.

Experience with these prior systems indicates that if the start valve ismaintained open, and consequently the actuating motor is maintained incommunication with the high pressure side of the system, after eitherthe accumulator is depleted of oil or the engine becomesself-sustaining, the displacement control element of the motorpump unitwill oscillate rapidly between large displacement positions at oppositesides of the zero displacement position. The reason for this is thateach of the events just mentioned causes a sudden, drastic reduction inthe pressure in the high pressure side of the system which makes itimpossible for the actuating motor to hold the ice control valve in itssupply position. As a result, the control valve shifts to its ventposition, the pressure in the control motor is suddenly dissipated, andthe positioning mechanism rapidly moves the displacement control elementover center. At this time, the motor-pump unit commences to dischargeiluid to the high pressure side of the system and to raise its pressure.When the pressure is restored to the level required to enable theactuating motor to reposition the control valve in its supply position,the control motor is suddenly subjected to the full pressure thenexisting in the high pressure side of the system. Therefore, this motorrapidly shifts the displacement control element back to the other sideof the zero displacement position and again reverses the direction of owthrough the motor-pump unit. In cases where the engine is running,oscillation of the displacement control element continues until thestart valve is closed and the control mechanism is set to hold thedisplacement control element at the proper side lof the zerodisplacement position for pumping operation. On the other hand, in thecase of abortive starts, wherein the engine does not attain aself-sustaining speed, the oscillation continues until the torque loadimposed by the motor-pump unit brings engine to rest. In either case,the oscillations produce pressure pulsations of large magnitudethroughout the entire system which create excessive stresses in, and caneven cause failure of, the various hydraulic components.

The object of this invention is to provide an improved starter system inwhich the severity of these oscillations of the displacement controlelement is greatly reduced. According to this invention, the systemincludes valving means for maintaining the actuating motor under theinitial pressure of the accumulator from the commencement of thestarting cycle until the start valve is closed. This improvement insuresthat the control valve will be maintained in its supply positionregardless of the pressure in the high pressure side of the system, andthus absolutely prevents this valve from suddenly changing the pressurein the control motor. Now, the control motor always responds directly tothe pressure in the high pressure side of the system during the startingcycle and does not produce the violent oscillations of the controlelement which have been encountered in the prior systems.

In the preferred embodiment of the invention, the valving means whichinsures proper operation of the actuating motor is incorporated in apackage which also includes the engine start valve and a common actuatorfor the two valve units. This package may also incorporate means forinsuring that the positioning mechanism for the displacement controlelement is set for motoring operation before the motor-pump unitcommences to develop torque. This feature precludes the undesirablemomentary reverse rotation of the engine at the instant the start cycleis initiated which can be encountered with the prior systems. Thepackaged arrangement of the start valve and the valve means whichcontrols the actuating motor is a desirable feature because it is lessexpensive than the alternative of providing separate valves, and, inaddition, it permits the invention to be incorporated in existingsystems in a routine manner by regular maintenance personnel.

The preferred and several alternative embodiments of the invention aredescribed herein in detail with reference to the accompanying drawingsin which:

FIG. l is a schematic diagram showing a hydraulic starting and pumpingsystem of the type disclosed in U.S. Patent 3,234,889 and incorporatingone form of the present invention. v

FIG. 2 is a schematic diagram of a similar starting and pumping systemincorporating a second form of the invention.

FIG. 3 is a schematic diagram of the preferred valve package.

FIG. 4 is a sectional view of the actual preferred embodiment.

FIGS. 5 and 6 are sectional views taken on lines 5-5 and 6-6 of FIG. 4.

FIG. 7 is a sectional view taken on line 7-7 of FIG. 6and FIG. 8 is asectional-view taken on lines 8 8 of FIG. 5 and lines 8--8 of FIG. 6.

The starting and pumping system shown in FIG. 1 is employed to startauxiliary and main turbine engines 11 and 12 and to provide hydraulicfluid under pressure to a utility circuit (not shown). The systemincludes an overcenter motor-pump unit 13 which is connected to driveand be driven by auxiliary engine 11, and which is provided with highand low pressure ports 14 and 15 that are connected, respectively, withmain conduit 16 and reservoir 17. Motive fluid for driving unit 13 as amotor is supplied by a gas-charged accumulator 18 through a circuitincluding conduits 16a, 1611 and 16 and controlled by the auxiliaryengine start valve 19. When unit 13 is being driven as a pump, it drawsfluid from reservoir 17 and discharges it under pressure into conduit16. This pressurized fluid may then flow to, and thus recharge,accumulator 18 through conduits 16b, 16C and 16a, or pass throughconduit 16d, main start valve 19 and conduit 16e to hydraulic starter21, and thus be used as the motive lluid for starting main engine 12, orpass through conduit 16f to the utility circuit.

The start valves 19 and 19' are of the pilotoperated type disclosed inU.S. Patent 3,203,165, and each has a main valve which is spring biasedto a closed position. When the pilot valve of either of the valves 19and 1'9' is shifted from its venting to its pressurizing position by theassociated solenoid 19a or 19a', the connection between the pilotedmotor and reservoir 17 is interrupted, and this motor is connected withthe conduit upstream of the start valve, that is, conduit 16a in thecase of valve 19, and conduit 16d in the case of valve 19. As a result,the piloted motor shifts the -main valve to open position. Venting ofeither piloted motor allows the spring to close the main valve.

The displacement of and direction of ow through unit 13 is controlled bycam plate 22 which is movable in opposite directions from theillustrated neutral or zero displacement position about the axis oftrunnion 23. Cam plate 22 is biased in the counterclockwise direction bya spring-motor assembly 24 including the coil compression spring 25 anda fluid pressure piston motor 26. The cylinder 27 of motor 26 isconnected to the piston 28 of a shifting motor 29 and carries a springseat having a longitudinal extension 31 which is arranged to abut theend of cylinder 32 when the two cylinders move toward each other. Thisextension 31 defines a limit stop for cam plate 22 which, during thepumping operation, prevents the cam plate from moving over center, i.e.,through the neutral position. The piston 28 is designed to move betweenthe illustrated position, in which it abuts stop 33, and a secondposition, in which its head abuts shoulder 34, for positioning assembly24 for motoring and pumping operations, respectively.

Cam plate 22 is moved in the clockwise direction about the axis oftrunnion 23 against the opposing bias of assembly 24 by a iluid pressurecontrol motor 35. Fluid is supplied to and exhausted from the workingchamber 36 of this motor through a pressure responsive control valve 37with which it is connected by conduit 38. Control valve 37 includes aninlet chamber 39 which is connected with the main conduit 16 throughconduit 16g, an outlet chamber 41 which communicates with conduit 38, anexhaust chamber 42 which is connected with reservoir 17, and a slidingvalve spool 43. This valve spool has supply and exhaust positions and anintermediate lap position, and is biased to the illustrated exhaustposition by a coil compression spring 44. In this position, land 45isolates outlet chamber 41 from inlet chamber 39, and a tlat 46 on land47 provides a flow path which connects outlet chamber 41 with exhaustchamber 42. The fluid pressure in chamber 39 acts upon the left end ofspool 43 and serves to shift this member to the right, rst to a lapposition in which lands 45 and 47 isolate chamber 41 from the other twochambers, and then to the supply position wherein land 47 continues toblock communication between chambers 41 and 42, and the flat 48extending across land 49 connects outlet chamber 41 with inlet chamber39.

The pressure in inlet chamber 39 required to hold valve spool 43 in thelap position against the opposition of spring 44 is termed the referencepressure, and Valve 47 includes two devices for changing this pressure.The rst, which raises the reference pressure, comprises a movable springseat 51 for spring 44, and a piston motor which includes the right sideof seat 51 and a working chamber 52. When working chamber 52 is vented,seat 51 assumes the illustrated low spring-load position, and, when theworking chamber is pressurized, the seat is moved to the left to a highspring-load position defined by stop 53. A conduit 54 connects workingchamber 52 with the pilot valve portion of main engine start valve 19',so that this chamber is vented and pressurized whenever the start valve19 is closed and opened, respectively. The second device for changingthe reference pressure acts to lower it from the normal value, and itcomprises a piston motor 55 including the piston 56 which abuts the leftend of spool 43, and a working chamber 57. The working chamber 57 isconnected with the pilot valve portion of auxiliary engine start valve19 through a pair of conduits 58 and 59 and the valving device 100provided by the present invention. As will appear below, this chamber 57is continuously subjected to the initial pressure in accumulator 18whenever valve 19 is open and, at all other times, it is vented toreservoir 17.

The piston 56 of motor 55 also serves as the valve spool of a selectorvalve 61 which simultaneously vents and pressurizes the working chambers26a and 29a of motors 26 and 29. This valve comprises the inlet chamber39 of control valve 47, an exhaust chamber 62 which is in continuouscommunication with reservoir 17, and an outlet chamber 63 which isconnected with working chamber 29a'through conduit 64. An axial passage28a in piston 28 interconnects working chamber 26a and 29a. Duringpumping operation, selector valve 61 assumes the illustrated positionwherein land 65 blocks communication between chambers 62 and 63, and theflat 66 extending across land 67 interconnects chambers 63 and 39.During thestarting operation, valve 61 shifts to the right to a positionin which land 65 blocks communication between chambers 63 and 39, andthe at 68 extending across land 69 connects outlet chamber 63 withexhaust chamber 62. Thus, selector valve 61 vents and pressurizes themotors 26 and 29 during the pumping and motoring operations,respectively. Since the diameter of the end land 56 of piston 56 isgreater than the diameter of lands 65 and 67, piston 56 will alwaysshift to the right when the pressures in working chamber 57 and inletchamber 39 are equal.

The valving device provided by the present invention includes a pair ofports 101 and 10-2 which are connected, respectively, with conduits 59and 58, and which are interconnected by passage 103 containing springbiased check valve 104. Check valve 104 is oriented to permit How fromconduit 59 to conduit 58, but to block ow in the reverse direction.Valving unit 100 also includes an exhaust port 105 which is incontinuous communication with reservoir 17 and which is connected withport 102 by a passage 106 containing a second spring biased check valve107. The biasing spring 108 of this check valve has a movable seat 109which is carried by the armature of a solenoid 111 so that the closingbias acting on the check valve changes as the solenoid is energized andde-energized. Solenoid 111 is connected in parallel with the solenoid19a of auxiliary engine start valve 19 in an energization circuit whichincludes battery 112 and which is controlled by the manually operatedstart switch 113 and a speed controlled switch 114 that responds to thespeed of engine 11.

Operation i Since U.S. Patent 3,234,889 contains a complete descriptionof the operation of the system shown in FIG. l, and the improvementsprovided by the present invention affect only the motoring mode ofoperation, the following description of operation will treat only thestarting cycle of engine 11.

Before commencement of the starting cycle, accumulator 1S is prechargedwith gas at a pressure of 1500 p.s.i. and is then charged with oil by ahand pump circuit (not shown). It is assumed that the fully chargedpressure of the accumulator is 3000 p.s.i., and that the three referencepressures of control valve 37 are 1500 p.s.i., 3000 p.s.i. and 4000p.s.i.

In order to start auxiliary engine 11 the operator closes switch 113 toenergize solenoid 19a and open start valve 19. This permits uid from theaccumulator 18 to ow into the high pressure port 14 of the motor-pumpunit through conduits 16a, 16h and 16, and also permits fluid ataccumulator pressure to pass to the working chamber 57 of motor 55through the pilot portion of valve 19, conduit 59, port 101, passage103, check valve 104, port 102 and conduit 58. Since solenoid 111 isenergized simultaneously with solenoid 19a, the load in spring 10S isnow sufficient to keep check valve 107 closed and prevent bleed off ofthe pressure in working chamber 57. The pressure of 3000 p.s.i. in thischamber causes motor 55 to shift selector valve 61 to a position inwhich it vents motors 26 and 29, and to shift control valve 37 to itssupply position in which control motor 35 is connected with main conduit16. As a result, control motor 35 moves cam plate 22 in the clockwisedirection to its maximum displacement position at the motoring side ofneutral and maintains it in that position against the opposing bias ofspring 25.

The fluid delivered to motor-pump unit 13 causes it to develop torqueand accelerate engine 11. As the engine accelerates, the pressure of theuid delivered by accumulator 19 progressively decreases from its initialvalue of 3000 p.s.i. However, this change in pressure is not reected inworking chamber 57 because the check valve 104 closes as soon as thepressure in conduit 59 begins to drop below the initial charge pressureof the accumulator. Therefore, as along as solenoid 111 is maintainedenergized and check valve 107 is held closed, the pressure in workingchamber 57 remains at 3000 p.s.i. and valves 37 and 61 remain in theirsupply and vent positions, respectively` Because of this, the pressurein working chamber 36 of control motor 3S will be substantially the sameas the pressure in main conduit 16 throughout the starting cycle.

Under normal conditions, engine 11 will have been ignited and will haveachieved self-sustaining operation before accumulator pressure decreasesto 1500 p.s.i. and the accumulator is depleted of oil. Since controlmotor 35 is dimensioned to hold cam plate 22 in the maximum displacementposition as long as the pressure in its working chamber 36 is above 1500p.s.i., it follows that the cam plate 22 in the normal case will notmove away from its maximum displacement position during the startingcycle. When the engine reaches a self-sustaining speed, switch 114automatically opens the holding circuit for switch 113 and allows thisswitch in tum to open and deenergize solenoids 19a and 111.De-energization of solenoid 19a allows auxiliary engine start valve 19to close and interrupt the flow of iluid from the accumulator 18 to highpressure port 14. On the other hand, de-energization of solenoid 111reduces the load in spring 108 and permits check valve 107 to open underthe action of pressurized oil trapped in working chamber 57. Therefore,this oil may now escape to reservoir 17 through conduit 58, port 102,passage 106 and port 105. Since engine 11 is now driving motor-pump unit13 as pump, and cam plate 22 is still at the motoring side of theneutral position, unit 13 will commence to evacuate 4main conduit 16. Asa result, the pressure in this conduit and in the working chamber 36 ofcontrol motor 35 will decrease well below 1500 p.s.i., and spring 25will move cam plate 22 in the counterclockwise direction to a smalldisplacement position at the pumping side of the neutral position. Atthe same time, spring 44 will return valves 36 and 61 to theirillustrated vent and supply positions, repsectively. As soon as camplate 22 moves over center, unit 13 cornmences to discharge oil underpressure to conduit 16 and thus quickly restores its pressure to 1500p.s.i. As this is happening, selector valve 61 transmits system pressureto shifting motor 29 and causes it to move the spring-motor assembly 24to its pumping position wherein the stop dened by extension 31 iseffective to prevent the cam plate 22 from moving back to the motoringside of neutral. Cam plate 22 will now assume a position in which thedisplacement of unit 13 is equal to the rate of leakage from the system.At this time the pressure in inlet chamber 39 of valve 37 will movespool 43 to its lap position.

ln the abnormal case, where accumulator 18 is given an inadequate gasprecharge or is charged with an insuicient quantity of oil from a startcycle, the engine 11 does not achieve a self-sustaining speed by thetime accumulator 18 is depleted of oil. When this happens, the engine11, which has considerable momentum, will cornmence to coast and driveunit 13 as a pump. Since cam plate 22 is at the motoring side of neutralposition, unit 13 will draw fluid from conduit 1'6 and discharge it toreservoir 17. This pumping action will quickly decrease the pressure inconduit 16 toward zero. In the prior system of Patent 3,234,889, whereincond-uit 58 is in constant, direct communication with conduit 59, thischange in pressure causes valves 37 and 61 to shift to their exhaust andsupply positions, respectively. This action resulted in sudden ventingof working chamber 36, and in sudden pressurization of working chambers26a and 29a, and caused the controls for cam plate 22 to move it rapidlyto a large, and perhaps even the maximum, displacement position at thepumping side of neutral. Unit 13 would then commence to discharge oil toconduit 16 and recharge accumulator 18. As soon as the pressure inconduit 16 was restored to 1500 p.s.i., valves 37 and 61 would shiftback to their supply and vent positions, respectively, and suddenlyapply full system pressure to working chamber 36 and vent workingchambers 26a and 29a. Now the controls would shift cam plate 22 rapidlyback to a rather large displacement position at the motoring side ofneutral. At this point, unit 13 would again commence to act as a motorand drive engine 11. However, as soon as accumulator 18 was againdepleted of oil, the controls would produce another violent oscillationof cam plate 22. These oscillations continued until the engine 11 cameto rest, and, since they were accompanied by severe pressure pulsationsin the conduits connected with ports 14 and 15, there was ampleopportunity for the system components to be damaged.

In contrast to this, the valving device provided by the presentinvention holds the initial charge pressure of accumulator 18 in workingchamber 57, and thus enables motor 55 to keep valves 37 and 61 in theirsupply and eX- haust positions, respectively, as long as solenoid 111remains energized. Therefore, in this system the pressure changes inconduit 16 always are reflected directly in working chamber 36, andcannot cause valve 61 to pressurize motors 26 and 29. With thisarrangement, motor 35 and spring 25 still move the cam plate 22 back andforth across the neutral position during an abortive start, but the rateof movement of the cam plate and the amplitude of its oscillation aremuch less than in the prior system. Actual experience with thisimprovement shows that it reduces to tolerable levels the pressurepulsations encountered during abortive starts.

Another abnormal case in which the invention effects an improvementconcerns starts in which the switch 114 fails to open when the engine 11reaches a self-sustaining speed. This situation produces the same effectas an abortive start, except that the unit 13 operates continuously as apump which discharges alternately through ports 14 and 15, and, sincethe engine is running under its own power, the oscillations of cam plate22 continue until start switch 113 is opened manually. As in the case ofthe abortive start, the valving device 100 so reduces the severity ofthese oscillations that the pressure pulsations are kept withintolerable limits.

The FIGURE 2 embodiment The system shown in FIG. 2 is generally the sameas the one of FIG. l, except that here the valves 204 and 207, whichcorrespond to check valves 104 and 107 embodied in the device 100 ofFIG. 1, are combined with the auxiliary engine start valve in a singlepackage 200. In this case, the passage which interconnects ports 1 and202 has two enlarged sections 203m and 203b, which are separated by themain poppet 215 of the start valve, and the latter section leads to adelivery port 216 as well as to check valve 204. The elements 201, 203a,203b and 216 dene the supply path through which motive fluid isdelivered to the motor-pump unit 13. The main poppet 215 is urged towardits seat 217 by a coil compression spring 218 and by the fluid pressurein a pilot chamber 219 which acts upon its upper surface 221. The poppetis shifted in the opening direction against this bias by the pressure inpassage section 203a which acts upon the annular shoulder 222. Pilotchamber 219 is connected with inlet port 201 by passage section 203a anda restricted passage 223 formed in the poppet, and is connected withexhaust port 205 through a path comprising passages 224 and 225 andcontrolled by a pilot valve in the form of spring biased check valve226. This check valve is oriented to normally block flow from pilotchamber 219, but is opened by push rod 227 whenever solenoid 211 isenergized to hold valve 207 closed.

The valving package 200 is incorporated in the system by connectingports 202 and 205 with conduit 58 and reservoir 17, respectively, byconnecting port 201 directly with accumulator 18 through conduit 16a,and by connecting port 216 with the conduits 16b and 16 leading to thehigh pressure port 14 of motor-pump unit 13. This last mentionedconnection includes a check valve 228 which permits ow from, b-ut notinto, passage section 203b. When the FIG. 2 system is in standbycondition, solenoid 211 is de-energized and valves 204, 207 and 226assume their illustrated positions. Although the fluid in passagesection 203g is subjected to the full charge pressure of accumulator 18,and thus tends to open main poppet 215, the uid in pilot chamber 219 isunder the same press-ure and acts on a larger reaction surface, namelyupper surface 221. Therefore, the net pressure force acting on thepoppet 215 supplements the biasing force developed by spring 218 andholds poppet 215 tightly against its seat 217. This precludes leakagefrom accumulator 18.

In order to start engine 11, the start switch (not shown) is closed toenergize solenoid 211 and cause it to close and open the valves 207 and226, respectively. Opening of valve 226 allows oil to escape from pilotchamber 219 to reservoir 17 at a rate greater than that at which it canenter this chamber through restricted passage 223. As a result, thepressure in chamber 219 decreases below that in passage section 203a,and the net pressure force acting on poppet 215 shifts this member toopen position against the opposition of spring 218. Fluid underaccumulator pressure now is delivered to the high pressure port 14 ofunit 13 via passage section 203]), port 216, and con- 8 duits 16b and16, and to the working chamber 57 of actuating motor 55 through passagesection 20312, check valve 204, port 202 and conduit 58. The FIG. 2system now effects starting of engine 11 in the same way as the FIG. 1system.

During a normal starting cycle, solenoid 211 is de-energized as soon asengine 11 becomes self-sustaining. Therefore, at this time, valves207and 226 are allowed to open and close, respectively. As soon as valve226 closes, the pressures in chamber 219 and passage section 203aequalize, and main poppet 215 closes. Simultaneously, opening of Ivalve207 automatically sets the controls for unit 13 to their pumpingcondition. Therefore, this unit can now recharge the accumulator 10 andperform its other pumping functions. In the case of an abortive start ora failure of switch 114, the valving device 200 serves to preventviolent oscillations of the cam plate of unit 13 in the way as itscounterpart in FIG. l. While the cyclic variations in the pressure inconduit 16b during these conditions are reflected in passage section203a, and may cause closing and opening movement of main poppet 215,this will not adversely affect the performance of the motorpump unit 13or the starting system.

The preferred embodiment The preferred valving device 300, which isillustrated schematically in FIG. 3, is similar to device 200 in that itincorporates the start valve and the check valves necessary to trapfluid in actuator motor 55. However, in this embodiment, the pathbetween the pilot chamber 319 of the start valve and exhaust port 305includes a flow restrictor 329, and the inlet and outlet ports 301 and302 are interconnected by a path which comprises passages 331 and 332and which is controlled by check valve 333 rather than main pop-pet 315.The check valve 333 normally blocks flow from port 301 to port 302, butis mechanically unseated to permit such flow by an actuating rod 334which is operated by solenoid 311. Thus, when the solenoid is energizedto effect opening of pilot valve 326 and closure of the vent valve 307,it simultaneously opens valve 333 and permits fluid under accumulatorpressure to flow to the actuating motor 55 through a path comprisingport 301, passages 332 and 331, valve 304, outlet port 302 and conduit58.

It will be observed that, since spring 25 in motor-pump unit 13 biasescam plate 22 to a position at the pumping side of neutral when thestarting system is at rest, unit 13 will momentarily rotate engine 11 inthe reverse direction at the commencement of the starting cycle if itcommences to develop torque before the controls have y been energized tomove the cam plate over center. The preferred embodiment eliminates thiscondition. This is accomplished by so sizing flow restrictor 329 that,when valves 326 and 333 are first opened, fluid under accumulatorpressure is transmitted to outlet port 302 before the pressure in pilotchamber 319 can decrease suliciently to permit opening of main poppet315. As a result of this delay, actuating motor 55 Will have time toshift valves 37 and 61 to the positions required for motoring operationbefore high pressure port 14 is subjected to full accumulator pressure.Since shifting of these valves vents motors 26 and 29 and places motor35 in direct communication with conduit 16, and since the pressurerequired by motor 35 to shift the cam plate over center is much lessthan the pressure required by unit 13 to satisfy the break away torquerequirement of engine 11, it should be apparent that, when main poppet315 opens and the pressure in conduit 16 rises, motor 35 will move thecam plate to the motoring side of neutral before the unit 13 commencesto rotate. Thus, the valving device 300 precludes any reverse rotationof engine 11.

It should -be noted that since outlet port 302 in the FIG. 3 embodimentis isolated from the high pressure conduit 1611 when solenoid 311 isde-energized, systems in- 9 corporating this form of the invention donot require the check valve 228 used in FIG. 2.

The details of the actual valving device 300 are shown in FIGS. 4-8,wherein the counterparts of the components shown in FIG. 3 are, as faras possible, identified by the same reference numerals. While theconstruction of this embodiment will be apparent from an inspection ofthese gures, it will be helpful to describe specifically the followingflow paths shown schematically in FIG. 3:

(l) The path connecting inlet port 301 with check valve 333 is shown inFIG. 4 and comprises annular groove 303a formed in the outer peripheryof sleeve 335, drilled housing passage 332a, annular housing chamber332b, longitudinal passage 332e defined by a fiat on the outer peripheryof sleeve 336, and radial passages 332d and 332e.

(2) The path connecting check -valve 333 with port 302 is shown in FIGS.4 and 5 and comprises axial passage 331a formed in block 337, drilledpassage 331b, annular housing groove 331e, drilled housing passages331d, 331e and 331f, axial passage 331g formed in the seat sleeve 338,check valve 304, and the axial passage 331k formed in fitting 339.

(3) The path connecting outlet port 302 with exhaust port 305 is shownin FIGS. 5-8 and comprises axial passage 33111, radial passages 306a,and 30612, longitudinal passage 306C defined by a fiat on the outerperiphery of sleeve 341 (see FIG. 5), annular housing chamber 306a',drilled housing passage 306e, housing chamber 306f (see FIGS. 6 and 8),slot 306g formed in plug 342, axial passage 30611 in seat block 343,check valve 307, radial passages 3061' and 3061' formed in sleeve 344,chamber 306k, drilled passage 3061, annular housing chamber 306m, anddrilled housing passage 306n (see FIG. 7).

(4) The path connecting pilot chamber 319 with exhaust port 305 is shownin FIGS. 4 and 7 and comprises slot 325a formed in spring seat 345,check valve 326, chamber 325b formed in insert 346, drilled passages325C and 325d formed in Iblock 347, annular housing chamber 325e, anddrilled housing passage 30611. In this embodiment, either passage 325aor passage 325:1 may serve as the flow restrictor 329 of FIG. 3.

Although We have referred to two specific starting systems in which theinvention may be used, it should be understood that there are othertypes of hydraulic starting systems which present the problem which theinvention solves. One such system which deserves mention is disclosed inU.S. Patent 3,106,057, granted Oct. 8, 1963. In cases where the camplate of the motor-pump unit in this prior system is provided with anunbalanced control, i.e., a control which automatically moves the camplate to a pumping position rather than the neutral position when theaccumulator is fully discharged, intolerable oscillations of the camplate can occur under the two abnormal conditions mentioned earlier. Theseverity of these oscillations can be reduced by incorporating thepresent valving device in conduit 75 of the patent so that it serves tomaintain motor 53 at'the initial charge pressure of the accumulatorthroughout the starting cycle.

As stated previously, the drawings and description relate only to thepreferred and several alternative embodiments of the invention. Sincethe structures of these embodiments can be changed in many respectswithout departing from the inventive concept, the following claimsshould provide the sole measure of the scope of the invention.

What we claim is:

1. A valving device (100, 200 or 300) comprising a housing containing(a) three ports (101, 102, 105; 201, 202, 205 or 301,

302, 305); (b) a first passage (103; 203a, 203b or 303a, 331,

332) interconnecting the first and second ports;

(c) a check valve (104, 204 or 304) in the first passage arranged toprevent flow toward the first port;

(d) a second passage (106, 206 or 306) interconnecting the second andthird ports;

(e) a second valve (107, 207 or 307) for opening and closing the secondpassage; and

(f) an actuator (111, 211 or 311) for operating the second valveindependently of the pressure at the first port and of the rate of fiowfrom the first port to the second port.

2. A valving device (200) as defined in claim 1 which also includes (a)a third valve (215) interposed in the first passage between the checkvalve (204) and the first port (201) and arranged to open and close thatpassage;

(b) means (218) biasing the third valve closed;

(c) a fourth port (216) connected with the first passage at a pointbetween the third valve (215) and the check valve (204);

(d) a third passage (219, 224, 225) interconnecting the first and thirdports and containing a ow restriction (223);

(e) a fourth valve (226) interposed in the third passage between theflow restrictor (223) and the third port (205), the fourth valve beingoperated by said actuator (211) so that it opens and closes the thirdpassage as the the second valve (207) closes and opens, respectively,the second passage (206);

(f) means (222) responsive to the pressure in the third passage lbetweenthe first port (201) and the flow restrictor (223) for urging the thirdvalve (215 in the opening direction; and

(g) means (221) responsive to the pressure in the third passage betweenthe flow restrictor (223) and the fourth valve (226) for urging thethird valve (215) in the closing direction.

3. A valving device (300) as defined in claim 1 which also includes (a)a fourth port (316);

(b) a third passage (303a, 303b) connecting the fourth port (316) withthe first port (301) and controlled by a third valve (315);

(c) a fourth passage (319, 324, 325) interconnecting the first and thirdports (301, 305) and containing a flow restrictor (323);

(d) means (318) biasing the third valve (315) toward closed position;

(e) a fourth valve (326) interposed in the fourth passage between theflow restrictor (323) and the third port (305) `for controlling fiowthrough this passage;

(f) a fifth valve (333) interposed in the first passage (30311, 331,332) between the first port (301) and the check valve (304) forcontrolling flow through this passage;

(g) means responsive to the pressure in the fourth passage between thefirst port (301) and the flow restrictor (323) for urging the thirdvalve (315) in the opening direction;

(h) means (321) responsive to the pressure in the fourth passage betweenthe flow restrictor (323) and the fourth valve (326) for urging thethird valve (315) inthe closing direction; and

(i) means connecting the fourth (326) and fifth (333) valves with saidactuator (311) so that these two valves are opened and closed,respectively, as the second valve (307) is closed and opened,

(j) the restriction to flow through the fourth passage from the flowrestrictor (323) to the third port (305) being greater than therestriction to flow through the first passage from the first port (301)to the second port (302).

4. A valving device (300) as defined in claim 3 wherein (a) the second,fourth and fifth valves (307, 326, 333) are spring biased check valves,each valve having a stationary seat and a movable head whichis biased bya spring toward the seat, the fourth and fifth valves l(326, 333) beingOriented to prevent flow from the irst port (301), and the second valvev(307) being oriented to prevent fiow from the third port (305); and

(b) the actuator (311) comprises means (309, 327, 324) for mechanicallymoving the heads of the fourth and fth valves (326, 333) away from theirseats While simultaneously increasing the load in the biasing spring(308) of the second valve (307), and for'allowing the heads of thefourth and fifth valves (326, 333) to move toward their seats whilesimultaneously decreasing the load in the spring (308) of the secondvalve (307 References Cited UNITED STATES PATENTS McKee 137-609 XR Betz137-609 XR Tear 137-608 XR Baker 137-609 XR Guinard 137-609 XR Watson137-609 XRl Froshe 137-609 XR Suechting 137-609 Doolittle et al. 137-609XR SAMUEL SCOTT, Primary Examiner

